The present invention relates generally to structural members and more particularly to a strong yet lightweight hollow structural member and a method for its formation.
In the design and fabrication of the various types of structural members that are employed in the aerospace industry, it is frequently desirable to minimize the weight of the device by incorporating a hollow chamber into the structural member. One drawback associated with this approach is that the tubular or extruded components that are typically utilized in the fabrication of light weight structural members are difficult to mechanically fasten to other structures or devices as the clamping force that is generated by the mechanical fastener is often of sufficient magnitude to crush the tubular or extruded component.
One solution that has been proposed for resisting the tendency for the mechanical fastener to crush the tubular or extruded component is the use of metallic support structures or potting compounds to facilitate the transmission of load across the tubular or extruded component through a path that has sufficient strength and cross-sectional area to prevent the clamping force from crushing the tubular or extruded component. The drawbacks associated with both conventionally-installed metallic support structures and potting compounds are similar in that their placement within the tubular or extruded component requires that the tubular or extruded component be fabricated in several pieces to permit the support structure or potting compound to be introduced and accurately positioned within the hollow interior. A typical design incorporating this concept is illustrated in FIG. 1.
As illustrated, the structural member 2 includes a first shell member 3, a second shell member 4, a plurality of support structures 5 and a plurality of mechanical fasteners 6, which are typically rivets. In fabricating the structural member 2, the support structures 5 are positioned within an internal cavity 3a formed in the first shell member 3 and fastened thereto with several of the mechanical fasteners 6. The second shell member 4 is then positioned over the first shell member 3, thereby encapsulating the support structures 5 within the hollow cavity defined by the first and second shell members 3 and 4. The remaining mechanical fasteners 6 are then employed to fixedly couple the second shell member 4 to the first shell member 3. The degree of overlap between the first and second shell members 3 and 4 that is necessary to permit these two components to be coupled together, as well as the use of mechanical fasteners 6 to both position the support structures 5 and fasten the first and second shell members 3 and 4 together, adds considerable weight to the structural member 2.
Accordingly, there remains a need in the art for a structural member and a method for its construction wherein one or more support structures are accurately positioned and secured within the hollow interior of a tubular or extruded component without the use of mechanical fasteners.
In one preferred form, the present invention provides a reinforced structural member having a tubular member and a support structure. The tubular member has a sidewall that defines a hollow interior portion. The support structure is formed from a composite material and bonded to the sidewall in at least two predetermined locations. The support structure is positioned within the tubular member and configured to transmit force between the predetermined locations so as to prevent the tubular member from being crushed in response to the application of a force of a predetermined magnitude to the tubular member.
In another preferred form, the present invention provides a method for fabricating a structural member. The method includes the steps of: providing a tubular member having a sidewall that defines a hollow interior portion; providing a support insert formed from a composite material, the support insert being configured to fit within the hollow interior and contact the sidewall in at least two predetermined locations; positioning the support insert within the hollow interior at a predetermined location; and bonding the support insert to the tubular member such that the support insert is operable for transmitting a load between the predetermined locations.